The present disclosure generally relates to resolving vergence-accommodation conflict (VAC) in multifocal head-mounted displays (HMDs), and specifically to decomposition of an image in a multifocal system.
Vergence-accommodation conflict (VAC) is a phenomenon that occurs to users of three-dimensional displays and virtual-reality (VR) headsets. In normal situations, eyes converge (rotate toward one another) to focus on closer objects and diverge (rotate away from one another) to focus on objects that are further away. Accommodation is coupled with convergence, and is the process where the lenses of the eyes focus on a close or far away object. In three-dimensional displays and VR systems, these two processes are decoupled. The eyes accommodate to the fixed distance of the screen of the headset, but still verge to the perceived distance of the virtual object. This decoupling can cause the user to feel uncomfortable, disoriented, or nauseous.
Building multiple focal planes into the three-dimensional display may reduce the effect of VAC by providing multiple image planes that together span the viewer's accommodation range. Using the multiple focal planes, a single image can be decomposed across the multiple displays to simulate the relative focal blur, sharpness and depth that the user's eye would naturally produce. However, decomposition of an image across multiple displays is computationally costly and conventional techniques may not be able to render image content across the multiple displays in real-time. As a consequence, conventional decomposition techniques are not able to dynamically respond to eye movement, and are thus unable to correct for misalignment of an eye with the multiple focal planes or changes to an eye's vergence or accommodation. In addition, existing multifocal displays assume a single, fixed viewpoint directly perpendicular to the display surface, and do not provide ways to measure how the direction of a user's gaze effects the success of the decomposition.